Articulated hitch coupler

ABSTRACT

An articulated coupler permits vertical displacement of a towed vehicle relative to a towing vehicle while preventing lateral or horizontal displacement of the towed vehicle relative to the towing vehicle. Multiple linkage arms provide coupling for special configuration towed vehicles such as short wheel-mounted lifts that experience torsional forces due to the presence and absence of loads on the lift.

PRIORITY CLAIM AND CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of U.S. ProvisionalApplication No. 61/794,249, filed on Mar. 15, 2013, and U.S. ProvisionalApplication No. 61/792,565, filed on Mar. 15, 2013, and the entiredisclosure of each is incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTINGCOMPACT DISK APPENDIX

Not applicable.

BACKGROUND

1. Technical Field

This invention relates generally to apparatus, systems, methods,techniques, etc. for coupling a motor vehicle or other pulling vehicleto a wheeled trailer or other towed cargo.

2. Description of Related Art

A variety of uses have arisen for pulling or towing a trailer or other“towed vehicle” to accompany a motor vehicle or other “towing vehicle.”Hitching a towed vehicle to a towing vehicle has been accomplished by amultiplicity of different structures and techniques. In some settings itis desirable to limit the manner and range of linear and rotationaldisplacement permitted for a towed vehicle. Apparatus, systems, methods,techniques, etc. that provide improved coupling of a towed vehicle to atowing vehicle while limiting relative movement of the two vehicles toonly vertical displacement would represent a significant advancement inthe art.

SUMMARY

The present invention is readily understood by the following detaileddescription in conjunction with the accompanying drawings. Embodimentsof an articulated, self-adjusting coupler include a rotational linkageusing two or more (and in some embodiments four) linkage arms thatpermit vertical rotational displacement of a towed vehicle relative to atowing vehicle, but otherwise prevent undesirable movement and/orstresses during use of the towed vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be readily understood by the followingdetailed description in conjunction with the accompanying drawings,wherein like reference numerals designate like structural elements.

FIG. 1 is a perspective view of a motor vehicle towing vehicle and atrailer towed vehicle coupled together using an articulated coupleraccording to one or more embodiments of the present invention.

FIGS. 2A-2D are side views of a motor vehicle towing vehicle and atrailer towed vehicle coupled together using an articulated hitchcoupler according to one or more embodiments of the present invention.

FIG. 3 is a perspective view of a trailer towed vehicle to which ismounted an articulated hitch coupler according to one or moreembodiments of the present invention.

FIG. 4 is an end view of a trailer towed vehicle to which is mounted anarticulated hitch coupler according to one or more embodiments of thepresent invention.

FIG. 5 is a side view of a trailer towed vehicle to which is mounted anarticulated hitch coupler according to one or more embodiments of thepresent invention.

FIG. 6 is a bottom view of a trailer towed vehicle to which is mountedan articulated hitch coupler according to one or more embodiments of thepresent invention.

FIG. 7 is a side sectional view of a trailer towed vehicle to which ismounted an articulated hitch coupler according to one or moreembodiments of the present invention.

FIG. 8 is a perspective view of an articulated coupler according to oneor more embodiments of the present invention.

FIG. 9 is an exploded view of an articulated coupler according to one ormore embodiments of the present invention.

FIG. 10 is a side view of an articulated coupler according to one ormore embodiments of the present invention.

FIG. 11A is a top cross-sectional view of an articulated coupler usingsolid bars as linkage arms according to one or more embodiments of thepresent invention, taken along the line 11-11 of FIG. 10.

FIG. 11B is a partial top cross-sectional view of an articulated hitchcoupler using tubes as linkage arms according to one or more embodimentsof the present invention, taken along the line 11-11 of FIG. 10.

FIG. 12A is a side view of an articulated hitch coupler according to oneor more embodiments of the present invention wherein the trailer channelis rotated upward relative to the vehicle channel.

FIG. 12B is a side view of an articulated hitch coupler according to oneor more embodiments of the present invention wherein the trailer channelis rotated downward relative to the vehicle channel.

FIG. 13A is a side view of an articulated hitch coupler according to oneor more embodiments of the present invention wherein the hitchingweldment comprising a draw bar and vehicle channel is in a firstvertical orientation relative to the trailer channel.

FIG. 13B is a side view of an articulated hitch coupler according to oneor more embodiments of the present invention wherein the hitchingweldment comprising a draw bar and vehicle channel is in a secondvertical orientation relative to the trailer channel and using the samevehicle channel bushings as shown in FIG. 13A.

FIG. 13C is a side view of an articulated hitch coupler according to oneor more embodiments of the present invention wherein the hitchingweldment comprising a draw bar and vehicle channel is in the secondvertical orientation relative to the trailer channel and using differentvehicle channel bushings as shown in FIG. 13A.

FIG. 14A is a side view of an articulated hitch coupler using torsionsprings according to one or more embodiments of the present invention.

FIG. 14B is a side view of an articulated hitch coupler using extensionsprings according to one or more embodiments of the present invention.

FIG. 14C is a side view of an articulated hitch coupler usingcompression springs according to one or more embodiments of the presentinvention.

DETAILED DESCRIPTION

The following detailed description of the invention, including theFigures, will refer to one or more invention embodiments, but is notlimited to such embodiments. Rather, the detailed description isintended only to be illustrative. Those skilled in the art will readilyappreciate that the detailed description given with respect to theFigures is provided for explanatory purposes as the invention extendsbeyond such specific embodiments. Embodiments of the invention provideapparatus, systems, methods, techniques, etc. including and pertainingto (but not limited to) self-adjusting, articulated hitch couplingsystems for connecting a towed vehicle to a towing vehicle. Otherstructures and uses will be apparent to those skilled in the art afterconsidering the following disclosure and the Figures provided herewith.Embodiments of the present invention will be shown and explainedprimarily in connection with a coupler used to couple a motor vehicle toa trailer-based lift or the like. Some embodiments can be used inconnection with other towed vehicles and towing vehicles.

The Figures illustrate one or more embodiments of a self-adjustingtrailer coupler that can be used for coupling a powered towing vehiclesuch as an automobile, SUV, etc. to a wheeled towed vehicle such as atrailer or the like, though the present invention is not limited to onlythese types of towing vehicles and towed vehicles. Embodiments of theself-adjusting coupler accommodate articulation in both verticaldirections relative to the towing vehicle (up and down, or + and −),that is vertical displacement of the towed vehicle up or down relativeto the towing vehicle. This allows the towed vehicle to remain in anessentially identical “upright” orientation relative to the towedvehicle during vertical transitions, such as those encountered when amotor vehicle or the like ascends or descends a sloped driveway, ramp,etc. and/or when the towing vehicle and towed vehicle are on differentvertical levels. Some embodiments shown in the Figures and/or describedherein can accommodate shifts in the range of approximately 9 inches ineach vertical displacement direction (other embodiments can accommodateshifts of up to 11 inches), though other ranges of motion can berealized with adjustments to the dimensions and other characteristics ofthe components of the self-adjusting, articulated hitch couplerembodiments presented herein.

Most trailer configurations provide for an extended platform or the likeon which cargo can be loaded. The trailer platform typically extendswell back from the rear of a towing vehicle and provides adequatesurface area for distribution of cargo or orientation of a load so as toprovide the center of gravity of the load or cargo over or nearly overthe wheels or other supports. Thus even heavy loads do not exertinordinate torque forces on the hitching apparatus or other componentsother than the wheels/supports. Moreover, because the trailer platformtends to be relatively elongated, the trailer itself is not mounted tooclose to the towing vehicle. Weight is normally distributed on a trailerwith 70% of the load situated between the towing vehicle and the towedvehicle's wheels. In some articulated hitch coupler embodiments herein,˜80% of the load (e.g., on a loaded lift platform) can sit behind thetowed vehicle wheels, especially when the towed vehicle wheels areswiveled toward the towing vehicle and the lift platform is loaded. Inthis disclosure the terms “rearward,” “behind,” “frontmost,” “ahead,”“forward” and the like are used relative to the front and reardirections of a motor vehicle or other towing vehicle to which thearticulated hitch coupler and any towed vehicle are connected.

When a trailer or other towed vehicle is considerably shorter than thetypical trailer, centering of the load above the wheels/supports may notbe possible. Moreover, when the trailer platform is positioned rearwardof the wheels/supports, the loaded platform can in some cases exert aconsiderable torque force on the hitching apparatus, even for modestloads of a few hundred pounds. The challenges posed by substantialtorque from such configurations can be exacerbated by the use of casterwheels or other swiveling supports that can change the length of thelever-arm.

Some embodiments of the self-adjusting coupler disclosed and claimedherein are shown in use with a trailer-mounted lift that has theabove-noted characteristics—namely, swiveling wheels that are positionedbetween the motor vehicle hitching apparatus and a cargo platform thatis completely rearward of the wheel-ground engagement axis. While suchexamples help to illustrate advantages of the embodiments illustrated,the present invention is not limited solely to trailers or other towedvehicles that have one or all of these characteristics.

FIGS. 1 and 2A-2D show a motor vehicle 80 coupled to a personal mobilityvehicle lift 90 using a self-adjusting, articulated towing coupler 100that is shown in more detail in the Figures. In FIG. 2C, the towedvehicle, lift 90, is relatively lower than the towing motor vehicle 80,due to a difference in the vertical levels on which each sits. Theangular relationship of motor vehicle 80 to lift 90 in FIG. 2D achievesthis same type relative vertical displacement. Conversely, in FIG. 2B,towed vehicle 90 is relatively higher due to a different angulardisplacement.

In FIGS. 3-8, the motor vehicle 80 is not illustrated (the relativeposition of a towing vehicle can be determined by the location of thedraw bar 116)and more detail of the coupler 100 and lift 90 is visible.Lift 90 is supported by a pair of swiveling wheels 91 (or casters) andhas a generally horizontal lift platform 92 that can be raised andlowered using a powered mechanism 94. Swivel wheels 91 are shown inFIGS. 6 and 7 in their rearwardmost swivel position; that is, extendingaway from coupler 100 and towing vehicle 80 as far as wheels 91 canrotate. FIGS. 5 and 6 show swivel wheels 91 in various positions withthe wheels pivoting as indicated by arrows 93. In FIG. 5 both wheels 91are shown in phantom as being pivoted to their frontmost position, wherethe contact point of each wheel 91 with the ground is essentially aheadof the platform 92 and is generally beneath the power lifting mechanism94. These various wheel orientations change the ways in which the lift90 generates torque forces, especially when lift 90 is loaded withcargo, as shown in FIGS. 2A-2D. Lift mechanism 94 is mounted to a liftchassis 96 that has a generally planar, horizontal lower plate 98.

As seen in the Figures, a generally vertical trailer channel 102 that ispart of a towed vehicle unit is affixed to the underside of plate 98,for example by welding or any other suitable means. The platform 92 isviewed, relative to a motor vehicle 80 or the like, as extending“rearward” in the Figures (that is, the lift 90 is rearward of motorvehicle 80). This forward/rearward orientation, as defined and notedabove, will be used to describe other aspects of embodiments of thepresent invention.

In the Figures, trailer channel 102 of coupler 100 can be constructedfrom formed steel plate or the like and has a generally vertical channelthat opens “forward” toward the motor vehicle or other device to whichlift 90 is coupled. The trailer channel 102 can include 2 or morebushings 104 that are mounted across the vertical channel, as seen inthe Figures. In some embodiments more than 2 bushings 104 can be mountedin trailer channel 102 to provide adjustable mounting configurations, asdiscussed in more detail below. The bushings 104 are steel tubes orother structures configured to permit free rotation of two pairs oflinkage arms 106, 108 that are rotatably coupled to various bushings incoupler 100. Coupler 100 is shown in its “neutral” position in FIGS. 2Aand 5, wherein the linkage arms 106, 108 are in the positions they holdwhen the towed vehicle 90 and the towing vehicle 80 have no relativevertical displacement from one another. Each arm 106 of a pair of upperlinkage arms 106 is rotatably mounted to an upper trailer channelbushing 104 on the outside of trailer channel 102. Similarly, each arm108 of a pair of bottom linkage arms 108 is rotatably mounted to atrailer channel bushing 104 on the outside of trailer channel 102 belowthe mounting points of upper arms 106. Each linkage arm 106, 108 can beconstructed of appropriate material(s), e.g. being made of solid steelbar material, steel tubing, etc. The upper linkage arms 106 define anupper linkage arm plane and the lower linkage arms 108 define a lowerlinkage arm plane, the upper and lower linkage arm planes being parallelin some embodiments and non-parallel in other embodiments. Fewer than ormore than four linkage arms can be used in other embodiments, beingmounted to additional bushings, directly to the vehicle and trailerchannels or the like as needed. Linkage arms 106, 108 are mounted tobushings 104 using bolts 120. If steel tubes are used as linkage arms,then bushings can be used in the linkage arms (details of linkage armbushings 126, 128 can be seen in FIG. 11B, for example). In someembodiments the bolts and linkage arms 106, 108 (or bushings, if thelinkage arms are tubes) can be treated with an appropriate lubricant(e.g., grease, zerk fittings, or the like) and/or be constructed ofmaterials that permit very low friction engagement and rotation of bolts120 within each bushing 104, 114.

Despite the relatively free rotation of the linkage arms 106, 108relative to the vehicle channel 112 and trailer channel 102, the use ofbushings 104, 114 and bolts 120 provides a rigid, stable box-likestructure that does not permit undesirable angular displacement of thetowed vehicle relative to the towing vehicle (for example in the form ofa wobble or wagging of the towed vehicle or in the form of jackknifingof the towed vehicle during backing up of the towing vehicle). Thehorizontally (laterally) rigid configuration of coupler 100 in tandemwith the use of swiveling wheels 91 on the towed vehicle make shorttowed vehicles like lift 90 more easy to maneuver and less susceptibleto problems caused by ball hitches and other configurations that permitsuch horizontal angular displacement. Moreover, as noted below,embodiments of the articulated hitch coupler 100 herein convert avertically and horizontally rigid mortise and tenon hitch structure intoa coupling that accommodates substantial vertical displacement of thetowed vehicle relative to the towing vehicle.

The opposing ends of linkage arms 106, 108 are rotatably mounted toupper and lower vehicle channel bushings 114 on the outside of a vehiclechannel 112. Vehicle channel 112 is part of a towing vehicle unit and issimilar in construction to trailer channel 102, for example beingconstructed of formed steel plate and having 2 or more steel bushings114 mounted inside the rearward-open channel. Vehicle channel 112 can bewelded (or otherwise affixed) to a towing vehicle hitching structuresuch as a draw bar 116 that has a plurality of adjustment holes 118 formounting the draw bar 116 to a motor vehicle hitch receiver or the like.The embodiments of the coupler 100 herein allow a user to convert astandard, rigid mortise and tenon type of hitch configuration into ahitch that provides substantial vertical displacement of the towedvehicle relative to the towing vehicle while preventing horizontalangular displacement that comes with use of a standard ball hitch or thelike. Other motor vehicle mounting configurations can be used, dependingupon the type of towing vehicle and any mounting structures thereon.Moreover, various hitches (e.g., class I, II or III hitches) can beaccommodated using an interchangeable draw bar weldment that is easy toswap when the towed vehicle is going to be hitched to a different towingvehicle. Additional details of the coupler 100 can be seen in thevarious exploded view of coupler 100.

Rotatable securing of arms 106, 108 and bolts 120 to the trailer channel102 and vehicle channel 112 can be accomplished by various meansincluding bolts, axles, pins, or the like. In the Figures, bolts 120 areused in connection with washers and nuts to securely mount arms 106, 108to the trailer channel 102 and vehicle channel 112 while also allowingeasy adjustment of the mounting as well as transfer of the towed vehicle90 to a different towing vehicle that might have a different verticalprofile.

Using embodiments of the articulated hitch coupler disclosed herein,coupler 100 allows for rotation in both upward and downward directions,like a trailer hitch ball, while preventing lateral rotation (i.e.,about a vertical axis, like the yaw of an aircraft) and twisting (i.e.,about a front-to-back horizontal axis, like the roll of an aircraft).Moreover, the four linkage arms provide a rigid bracing that preventssubstantial linear displacement (though some minor front-to-back lineardisplacement naturally results due to the vertical rotation of the arms106, 108). Vertical displacement of the towed vehicle relative to thetowing vehicle can be seen in the detailed illustrations of coupler 100in FIGS. 12A and 12B, showing substantial upward and downward movementof trailer channel 102 relative to vehicle channel 112 for one or moreembodiments of the coupler.

Over-rotation of the linkage arms can be prevented in some embodimentsby employing mechanical stops 906, 908 on the linkage arms 106, 108 asshown in FIGS. 9, 12A and 12B. Each stop 906, 908 can be a smallrectangular piece of formed steel or the like with a suitable surface,such as a polymer or other material to prevent metal-on-metal damage andwear when a stop 906, 908 engages an opposing linkage arm 108, 106, asseen in FIG. 12A, where the trailer channel 102 has rotated to its fullupward extent relative to vehicle channel 112. In the embodimentsillustrated, one stop is used on each linkage arm; however, multiplestops can be used on linkage arm to achieve desired performancecharacteristics for the articulated hitch coupler. In addition topreventing damage and wear, stops 906, 908 can be used to preventlocking of the articulated hitch coupler in such maximum displacementpositions.

The geometry of the four linkage arm arrangement can be configured tooffset any inherent tendencies of a towed vehicle to rotate forwardand/or rearward. In one scenario, when a load is removed from the towedvehicle, the center of gravity of the towed vehicle shifts toward thetowing vehicle while the wheels (or other supports) define a fulcrumaxis. The result is a tendency for the towed vehicle 90 to tilt towardthe towing vehicle, that is for the upper part of lift 90 to rotateforward toward the towing vehicle 80. Likewise, when the platform 92 ofthe towed vehicle 90 is loaded, the center of gravity shifts away fromthe towing vehicle 80 (again with the towed vehicle's supports, e.g.wheels, defining a fulcrum axis), creating a tendency for the upper partof the towed vehicle 90 to tilt away from the towing vehicle, that is torotate rearward.

Some articulated hitch coupler embodiments use linkage arms 106, 108that are all parallel to one another, creating a parallelogram 4-barlinkage. However, parallel linkage arm configurations can lead to thelift 90 or other towed vehicle rotating toward or away from a towingvehicle, especially when the towed vehicle is relatively short and has aweight-bearing platform 92 or other structure that tends to affecttorsional forces substantially. Some embodiments of the articulatedcoupler thus utilize non-parallel mounting of the arms 106, 108, asdiscussed in more detail below.

The Figures illustrate wheel positions in which both wheels 91 are fullyswiveled forward, toward the towing vehicle 80. Other relativeorientations of the wheels can occur, for example (a) an orientation inwhich one wheel is rotated 90° “outboard” while the other wheel remainsrotated to the rear, under platform 92, (b) an orientation in which onewheel is rotated 90° “outboard” while the other wheel is swiveledforward, or (c) an orientation in which one wheel is rotated fullyforward while the other wheel is rotated fully rearward. These differentorientations illustrate the changing fulcrum axis defined by thelocations at which the wheels engage the ground. Those skilled in theart will recognize that these different orientations lead to differentweight distributions and resulting torque characteristics that depend onwheel position and the degree to which platform 92 is loaded. Theswiveling of wheels 91 provides improved maneuverability of the towedvehicle 90, but it can lead to relatively extreme weight distributionvariations and other issues that are not typically encountered withtraditional trailer configurations.

In some embodiments of an articulated hitch coupler, unequal spacingbetween rotation axes of the linkage arms 106, 108 can be used tocounteract the inherent tendencies of a towed vehicle 90 to rotatetoward or away from the towing vehicle 80. One such example of suchunequal spacing can include use of non-parallel linkage arms mountedbetween vehicle channel bushings and trailer channel bushings to createa slightly non-parallel orientation (e.g., out of parallel by 1° to 2°),which can allow the draw bar to move several degrees in a counteractingorientation, depending on whether the lift or other towed vehicle istending to rotate toward or away from the towing vehicle. Alternatedimensional and related aspects of this type of configuration can beemployed as well to provide longer or shorter linkage arms, greatervertical displacement capability, etc. The fulcrum axis of any torqueforces generated by cargo on a lift is defined by the where the trailerwheels engage the ground and the non-parallel linkage arm orientationcan counteract the tendency of the end of a draw bar up or down.

As seen in FIGS. 14A, 14B and 14C, to assist the coupler linkage arms106, 108 in returning to and maintaining their neutral orientation, oneor more springs or other biasing elements can be used. In FIG. 14A atorsion spring 820 can be mounted at one or more of the pivotablymounted ends of arms 106, 108. Each torsion spring 820 can bedual-directed. In FIG. 14B, diagonally mounted extension springs 830 canbe used as well —the springs 830 can be replaced in this configurationby dual acting counterbalance gas type springs, too. Finally, in FIG.14C, compression spring 840 can be mounted so that the spring 840compress as the linkage arms 106 and 108 get closer together. Suchspring or other biasing member configurations help prevent thearticulated coupler 100 from locking in a non-neutral position,especially when the coupler linkage arms are in one of the more extremepositions due to substantial vertical displacement between the towedvehicle and the towing vehicle.

Embodiments of the articulated hitch coupler shown in one or more of theFigures also provide a versatile mounting arrangement to accommodatediffering vertical profiles for a wide variety of towed vehicles andtowing vehicles. For example, the hitching weldment of the draw bar 116and vehicle channel 112 can be rotated 180° as seen in FIGS. 13B and13C, thus changing the height and mounting positions of four bushings114A, 114B, 114C and 114D. In FIG. 13B, bushings 114A and 114C are usedto mount link arms 106, 108, respectively, to trailer channel bushings104A and 104B. In FIG. 13C, a slightly lower vertical mounting isachieved when bushings 114B and 114D are used instead. When the drawbar/vehicle channel hitching weldment is rotated 180° as seen in FIG.13A, bushings 114A-D are in different positions and thus permit anotherset of vertical profile mounting arrangements with trailer channelbushings 104A and 104B.

Other configurations and embodiments are included in the articulatedhitch coupler disclosed herein. For example, one embodiment uses only asingle upper linkage arm 106 and a single lower linkage arm 108 that arerotatably held inside the trailer channel 102 and vehicle channel 112 byappropriate means. This embodiment maintains horizontal/lateralstability and rigidity by employing a bolt 120 or similar securing meansas well as using the side walls of the vehicle and trailer channels toprevent horizontal/lateral angular or other undesired displacement. Theside views of the four linkage arm embodiments also depict the twolinkage arm embodiments, with the exception that the ends of arms 106,108 would not be visible outside the vehicle and trailer channels fromsuch side views. Again, the dimensions, materials and othercharacteristics of such an embodiment can be adjusted to achieve desiredperformance from such an articulated coupler.

The many features and advantages of the present invention are apparentfrom the written description, and thus, the appended claims are intendedto cover all such features and advantages of the invention. Further,since numerous modifications and changes will readily occur to thoseskilled in the art, the present invention is not limited to the exactconstruction and operation as illustrated and described. Therefore, thedescribed embodiments should be taken as illustrative and notrestrictive, and the invention should not be limited to the detailsgiven herein but should be defined by the following claims and theirfull scope of equivalents, whether foreseeable or unforeseeable now orin the future.

What is claimed is:
 1. An articulated hitch coupler comprising: avehicle channel secured to a towing vehicle hitching structure, thevehicle channel comprising an upper bushing and a lower bushing mountedin the vehicle channel; a trailer channel configured to be secured to atowed vehicle, the trailer channel comprising an upper bushing and alower bushing mounted in the trailer channel; means for coupling thetowing vehicle unit to the towed vehicle unit, the coupling meanscomprising a plurality of linkage arms pivotable coupling the vehiclechannel bushings to the trailer channel bushings; wherein the couplingmeans is configured to permit vertical displacement of the trailerchannel relative to the vehicle channel and further wherein the couplingmeans is configured to prevent lateral angular displacement of thetrailer channel relative to the vehicle channel.
 2. The articulatedhitch coupler of claim 1 wherein the plurality of linkage armscomprises: a first upper arm having a first end pivotably coupled to theupper vehicle channel bushing and having a second end pivotably coupledto the upper trailer channel bushing; and a first lower arm having afirst end pivotably coupled to the lower vehicle channel bushing andhaving a second end pivotably coupled to the lower trailer channelbushing.
 3. The articulated hitch coupler of claim 2 wherein the firstupper arm and first lower arm are pivotably bolted inside the trailerchannel and inside the vehicle channel.
 4. The articulated hitch couplerof claim 2 wherein the plurality of linkage arms further comprises: asecond upper arm having a first end pivotably coupled to the uppervehicle channel bushing and having a second end pivotably coupled to theupper trailer channel bushing; and a second lower arm having a first endpivotably coupled to the lower vehicle channel bushing and having asecond end pivotably coupled to the lower trailer channel bushing. 5.The articulated hitch coupler of claim 4 wherein the first and secondupper arms are mounted on opposing external sides of the trailer channeland opposing external sides of the vehicle channel; further wherein thefirst and second lower arms are mounted on opposing external sides ofthe trailer channel and opposing external sides of the vehicle channel.6. The articulated hitch coupler of claim 5 wherein the first and secondupper arms are parallel to one another; further wherein the first andsecond lower arms are parallel to one another; and further wherein thefirst upper arm is parallel to the first lower arm.
 7. The articulatedcoupler of claim 6 further comprising a biasing element mounted to thecoupler and configured to resist vertical displacement of the trailerchannel relative to the vehicle channel.
 8. The articulated hitchcoupler of claim 7 further comprising a hitching weldment comprising adraw bar welded to the vehicle channel, wherein the hitching structurecomprises the draw bar, and further wherein the hitching weldment isvertically reversible.
 9. The articulated hitch coupler of claim 5wherein each linkage arm comprises a mechanical stop configured to limitlinkage arm rotation.
 10. An articulated hitch coupler comprising: atowing vehicle unit comprising a vehicle channel welded to a draw bar,the vehicle channel comprising an upper bushing and a lower bushingmounted in the vehicle channel; a towed vehicle unit comprising atrailer channel configured to be secured to a towed vehicle, the trailerchannel comprising an upper bushing and a lower bushing mounted in thetrailer channel; means for coupling the towing vehicle unit to the towedvehicle unit, the coupling means comprising four linkage armscomprising: a first upper arm having a first end pivotably coupled tothe upper vehicle channel bushing and having a second end pivotablycoupled to the upper trailer channel bushing; a second upper arm havinga first end pivotably coupled to the upper vehicle channel bushing andhaving a second end pivotably coupled to the upper trailer channelbushing; a first lower arm having a first end pivotably coupled to thelower vehicle channel bushing and having a second end pivotably coupledto the lower trailer channel bushing; and a second lower arm having afirst end pivotably coupled to the lower vehicle channel bushing andhaving a second end pivotably coupled to the lower trailer channelbushing; and biasing means mounted to the coupling means and configuredto resist vertical displacement of the trailer channel relative to thevehicle channel. wherein the coupling means is configured to permitvertical displacement of the trailer channel relative to the vehiclechannel and prevent lateral angular displacement of the trailer channelrelative to the vehicle channel.
 11. The articulated hitch coupler ofclaim 10 wherein the first and second upper arms comprise steel barsmounted on opposing external sides of the trailer channel and opposingexternal sides of the vehicle channel; further wherein the first andsecond lower arms comprise steel bars mounted on opposing external sidesof the trailer channel and opposing external sides of the vehiclechannel.
 12. The articulated hitch coupler of claim 11 wherein eachlinkage arm coupling to a bushing comprises a bolt permitting rotationof the linkage arm relative to the bushing to which it is pivotablycoupled.
 13. The articulated hitch coupler of claim 12 wherein the firstand second upper arms are parallel to one another; further wherein thefirst and second lower arms are parallel to one another; and furtherwherein the first upper arm is parallel to the first lower arm.
 14. Thearticulated hitch coupler of claim 10 wherein the biasing meanscomprises one or more springs mounted to coupling means to resistvertical displacement of the trailer channel relative to the vehiclechannel.
 15. The articulated hitch coupler of claim 10 wherein thevehicle unit is configured to be rotated 180° to provide multiple heightand mounting positions of the vehicle channel relative to the trailerchannel.
 16. The articulated hitch coupler of claim 15 wherein thevehicle channel further comprises third and fourth bushings mounted inthe vehicle channel to provide alternative coupling options for thelinkage arms.
 17. The articulated hitch coupler of claim 10 wherein thetowed vehicle unit comprises pivoting ground-engaging wheels or castersbelow a cargo platform.
 18. The articulated hitch coupler of claim 13wherein each linkage arm comprises a mechanical stop configured to limitlinkage arm rotation.
 19. An articulated hitch coupler comprising: avehicle channel secured to a towing vehicle hitching structure, whereinthe hitching structure comprises a draw bar welded to the vehiclechannel, the vehicle channel comprising an upper bushing and a lowerbushing mounted in the vehicle channel; a trailer channel configured tobe secured to a towed vehicle, the trailer channel comprising an upperbushing and a lower bushing mounted in the trailer channel; means forcoupling the vehicle channel to the trailer channel, the coupling meanscomprising four linkage arms comprising: a first upper arm having afirst end pivotably coupled to the upper vehicle channel bushing andhaving a second end pivotably coupled to the upper trailer channelbushing; a second upper arm having a first end pivotably coupled to theupper vehicle channel bushing and having a second end pivotably coupledto the upper trailer channel bushing; a first lower arm having a firstend pivotably coupled to the lower vehicle channel bushing and having asecond end pivotably coupled to the lower trailer channel bushing; and asecond lower arm having a first end pivotably coupled to the lowervehicle channel bushing and having a second end pivotably coupled to thelower trailer channel bushing; wherein each linkage arm coupling to abushing comprises a bolt permitting rotation of the linkage arm relativeto the bushing to which it is coupled; and biasing means mounted to thecoupling means and configured to resist vertical displacement of thetrailer channel relative to the vehicle channel; wherein the first andsecond upper arms comprise steel bars mounted on opposing external sidesof the trailer channel and opposing external sides of the vehiclechannel; further wherein the first and second lower arms comprise steelbars mounted on opposing external sides of the trailer channel andopposing external sides of the vehicle channel; and further wherein thecoupling means is configured to permit vertical displacement of thetrailer channel relative to the vehicle channel and prevent lateralangular displacement of the trailer channel relative to the vehiclechannel